10. Go into the retail dash and move the nuketown fix over to your hard drive.

11. Use XM360 to Unlock the fix (Scan All > Show DLC > Unlock DLC)
NOTE: Depending on which of the above links you use, the fix may already be unlocked and you'll see that in XM360.

12. After you do this, load up BO2 and allow the Nuketown to "Download." It will recognize that you have the DLC and it will stop the download by itself and it will say the download has been completed. You will no longer be stuck in the Download Nuketown Loop.